Generally, hoses having a rubber layer on the inner peripheral side are sometimes used for transmitting a high-temperature, high-pressure fluid (oil and the like) in construction machines, plant facilities and the like. Even if such hoses are used within the appropriate ranges set for their specifications, long term use of the hoses leads to gradual thermal aging of the rubber layer on the inner peripheral side due to the heat of the fluid. When excessive thermal aging of the rubber layer on the inner peripheral side is caused, there may be problems such as leaking of the fluid inside the hose from between the joint and the hose. To prevent such problems, it is effective to predict the remaining life of the hose or to diagnose the deterioration level of the hose on a regular basis to prevent the use of a hose with an excessively deteriorated rubber layer.
An example of a method for predicting the remaining life of the hose or diagnosing the deterioration level of the hose is a method of cutting out a part of the rubber layer on the inner peripheral side, measuring its physical properties, and using the results thereof. Further, proposed in JP2004271414A (PTL 1) is a method of attaching, to the base cap of the end of the hose, a rubber body for confirming deterioration which is made of the same material as the inner rubber layer of the hose in a state of being stretched by a predetermined amount, observing the rubber body for confirming deterioration from the outside to estimate the deterioration state of the inner rubber layer and detect hose deterioration.